This invention relates to surface-activated functional materials, which are usable as a high activity catalyst in catalytic oxidation reaction of hydrocarbons, methanol, carbon monoxide or the like, a high active electrocatalyst for fuel cells, an active material for cells, electronic materials and so on, and a method of producing the same.
As the functional material of this type, the prior art will be described below with reference to an electrode of a fuel cell. In the fuel cells, the thermal efficiency is very excellent as compared with the other electricity generators and also most of fuels are in the form of fluid and can continuously be fed as an active substance. As a result, the improved electrode in the fuel cells make it possible to largely prolong the limit of cell life without consumption and wastage of the active substance. Lately, such fuel cells have fairly been of interest and some of which have been put to practical use in specific fields such as spacecrafts, military parts and the like. However, the development of the fuel cell can be said to be halfway due to restrictions on the material of electrode and the like.
In electric cars, lead-acid batteries usually used have such drawbacks that the running distance per one charging is short, the battery weight is large and the charging time is long. In order to solve these drawbacks, the use of fuel cells has long been practiced, but there are no fuel cells suitable for electric cars in view of economy of fuel, service system and the like. If it is intended to use a hydrogen-oxygen fuel cell, which has been first practiced for spacecrafts, as a fuel cell for electric car, there is a difficulty on the storage of hydrogen source through the cell itself has excellent performances, so that such hydrogen-oxygen fuel cell is unsuitable for electric cars regarding the total system of the energy use.
Now, it is expected to utilize a fuel cell wherein methanol is directly used as a fuel instead of hydrogen. In this case, however, performances of a catalyst constituting the electrode for fuel cell are poor and a great amount of noble metal is used as the electrode catalyst, so that it is difficult to use the methanol fuel cell in electric cars in view of economic reasons.
The methanol fuel cell has a high activation polarization. In order to further improve the performances of the cell, noble metals such as platinum and the like are used as most excellent electrode catalysts, but there is a problem that high activity can not be obtained due to a strong poisoning of methanol itself to the catalyst. That is, it has been reported in Electrochimica Acta, Vol. 12, pp 1323-1343 (1967) that the following reaction formula is a rate-determining step in the mechanism of methanol oxidation: ##STR1## Therefore, in order to further elevate the activity for the above reaction, it has been estimated that an important key for the manufacture of the electrode catalyst is an enhancement a site adsorbing a hydroxyl group (OH.sup.-). In accordance with this estimation, it has hitherto been attempted to improve the oxidation performance of the electrode catalyst by adhering a heavy metal capable of adsorbing a compound containing oxygen such as in a hydroxyl group and the like at a relatively low potential to a surface of a noble metal such as platinum or the like (Japanese Patent laid open No. 143,040/75 and British Pat. No. 1,106,708). However, the electrode catalysts produced by the above attempt have poor reproducibility and are not practical. Particularly, in the method of Japanese Patent laid open No. 143,040/75 wherein the heavy metal is adhered to the noble metal previously adsorbed with hydrogen, the catalytic performance is not improved, but rather deteriorates as compared with that of the catalyst composed only of the noble metal such as platinum or the like.
Furthermore, since the noble metal such as platinum or the like to be used as the electrode catalyst is very expensive, the cost of the resulting fuel cell becomes expensive.